Faiza Tehseen

Several rock suites in Khyber Pakhtunkhwa (KP), Gilgit-Baltistan (GB), and Balochistan have been assessed as high-potential ones for diamond exploration,  said Muhammad Yaqoob Shah, Principal Geo-scientist at the Islamabad-based Global Mining Company. Discussing the presence of diamonds in the earthen vaults of Pakistan with WealthPK, he said in modern times, diamond mining was operational from every possible target. 

He said diamond was mined from unconventional diamondiferous host rocks. Geologically established genetic models and extensive field/laboratory observations strongly indicate diamond formations in Pakistan, he added. “Diamondiferous source mantle rocks may occur in Jijal complex rock suite. It is rich in garnet and pyroxene zones containing rare carbonate minerals with contents of titanium, nickel, chromium, and hematite ranging between 2763-9886ppm, 16-62 ppm, 14-109 ppm, and 10.90-15.20% respectively.

About 26 samples analysed from this area endorsed these findings. In the same area, ultramafic rocks are found belonging to Tethyan lower crust-upper mantle with units of pods and lenses of harzburgite, dunite, peridotites, and websterite containing chromium rich spinel in the olivine-rich rocks.’’

Within the ultramafic rock units of Chilas complex, a sound genetic model of diamondiferous rocks exists, i.e. olivine-orthopyroxene dominant rocks containing thin layers, streaks, and lenses of chromium spinel along with ilmenite and magnetite (a clear indicator mineral for the presence of diamondiferous rocks).

Continuing the discussion, Yaqoob said around the globe, at least 20 exhumed ultra-high-pressure terrains were found to contain diamonds/coesite. In these terrains with clear continental crust, some typical mineral assemblages are found in eclogite rocks with dominant magnesium but chrome-poor garnet and omphacite. This type of eclogite-bearing area is found in Kaghan. Here they occur as coarse-grained massive bodies, lenses, and thin layers. These rocks have a mineral assemblage of pyrope garnet, clinopyroxene, coesite, phengite, rutile, amphibole, epidote, ilmenite, and kyanite with minor zircon. Eclogite rocks are unique, as during their travel to the earth’s crust, they undergo all environments necessary for diamond formations.

Recent research shows that diamonds are found in ultramafic lamprophyres (rare potash-rich magmatic rocks, some of which have the intermediary chemical composition of alkaline silicate and carbonatites). These rocks are normally found as dykes, almost showing a complete range between carbonatites and silica-under-saturated alkaline rocks. This type of rock suite is comprised of strong diamond indicator minerals, i.e. chrome enstatite, pyrope, and chrome diopside, which are strong diamond indication minerals. This shows that they have traveled through the ‘diamond zone’ from the upper mental depths to the upper crustal regions.

Lamprophyres are exposed in Cherat ranges, Buner, Swat, Shalman, and in other tribal districts. However, small intrusions of ultra-potassic rocks piercing within the Loe-Shalman carbonatite complex, Khyber district, and in other tribal areas are hotspots to find diamonds in Pakistan.

The said intrusive bodies are established as high-level sub-volcanic magmatic rocks whereas petrographic mineralogical and chemical data extracted from three representative samples classify these rocks as belonging to ultrapotassic affinities with alkalis up to 8.75% and an average of 2.9% of magnesium oxide.

Diamondiferous rocks with kimberlite composition supported by their field relations, textures, and mineral chemistry have also been reported from Balochistan known as ‘Spangar Kimberlitic rocks’. They are exposed on the surface as conical and pipe-like bodies, plugs, linear dykes, and sills intruded in early Jurassic limestone. Petrographically, they are like ‘micaceous kimberlites’ containing phlogopite, olivine, perovskite, monticellite, serpentine, chlorite, apatite, calcite, chromian spinel, pectolite, amphibole, clinopyroxene, magnetite, titano-magnetite, and nepheline, etc.

Although the majority of diamonds are not formed within the kimberlites, many pieces of evidence point toward diamond origins in deep lithospheric conditions. Kimberlites/lamproites/eclogites occasionally ‘sample’ deep diamond-bearing mantle material and convey it to the surface, rapidly acting as transporting agent.

Chromitite and peridotite-bearing ophiolites are also documented as the host rocks of diamonds with a wide variety of highly reduced minerals, i.e. nickel, cobalt, manganese, Iron, silicon, cyanotrichite, etc. Traces of diamond are also found in podiform chromitite in Tibet, which means that possibilities may occur in areas with chromite-bearing ultramafic rocks, i.e. Waziristan. Diamonds are found in non-kimberlitic rocks of such areas in a few countries, e.g. China, Russia, Germany, Norway, and Indonesia.

For far-reaching industrial and socio-economic benefits, it is important for Pakistan to explore, establish and mine diamond like Russia, the Democratic Republic of Congo, Canada, Australia, Botswana, etc. Pakistan can earn a fortune by trading them directly or in value-added form.

Credit: Independent News Pakistan-WealthPk